The present invention relates generally to electronic circuit boards and, more particularly, to an improved electronic circuit board for enabling the stacking of electronic components.
Computer systems are increasingly used to perform more and more functions. As a result of this increase in functionality, the number of electronic components that are used within these computer systems correspondingly increases. Typically, such electronic components are mounted on a circuit board, which is then placed into a computer cabinet or chassis so as to allow the circuit board, and the electronic components mounted thereon, to interface with other circuit boards and electronic components. However, there is only a limited amount of space within a computer cabinet or chassis for accommodating circuit boards, and hence the electronic components mounted thereon. Thus, a need has arisen for developing schemes for increasing the density of electronic components on circuit boards.
Perhaps the first scheme that was developed for increasing the density of electronic components on circuit boards was the use of multilayer circuit boards. Such multilayer circuit boards allow more electrical signals to be routed between electronic components than what was previously possible using only single layer circuit boards. It follows that the density of electronic components is typically greater on a multilayer circuit board than on a single layer circuit board due to the increased number of electrical signals that may be routed between electronic components mounted on a multilayer circuit board.
While the use of multilayer circuit boards has allowed an increase in electronic component density, this increase in electronic component density has heretofore been limited by the amount of board surface area. That is, there is only a limited amount of surface area upon which electronic components may be mounted on a circuit board. With computer system functionality requirements, and hence electronic component requirements, only continuing to increase, there is a need to further increase electronic component density on multilayer circuit boards.
In view of the foregoing, it would be desirable to provide a technique for increasing electronic component density on circuit boards.
According to the present invention, a technique for increasing electronic component density on circuit boards is provided. In one embodiment, the technique is realized as an improved electronic circuit board for enabling the stacking of electronic components. The electronic circuit board has an electrically conductive signal layer formed on a dielectric layer, wherein the electrically conductive signal layer has a plurality of electrically conductive pads formed therein. The improvement comprises a cavity in the electronic circuit board extending through the electrically conductive signal layer and the dielectric layer. The cavity is sized to accommodate a first electronic component therein such that at least one first electrical connection may be formed between the first electronic component and a first portion of the plurality of electrically conductive pads, and at least one second electrical connection may be formed between a second electronic component, which is stacked over the first electronic component, and a second portion of the plurality of electrically conductive pads.
The first and second electronic components are typically either an integrated circuit component or a discrete component, and the type of electrical connections formed are dependent upon the type of component. For example, a solder bridge may form the first electrical connection between an electrically conductive contact pad and leadless contacts of the first electronic component.
In accordance with further aspects of the present invention, at least the lateral dimensions of the cavity are beneficially sized to directly coincide with at least the lateral dimensions of the first electronic component. This alleviates the need for any specialized positioning equipment, which has heretofore typically been required when mounting electronic components on circuit boards.
In accordance with further aspects of the present invention, the cavity is beneficially formed as a channel through which air may be forced for cooling at least the first electronic component.
In accordance with still further aspects of the present invention, wherein the cavity is a first cavity, wherein the dielectric layer is a first dielectric layer, wherein the electrically conductive signal layer is a first electrically conductive layer, wherein the electronic circuit board has a second electrically conductive layer disposed above the first electrically conductive layer within the electronic circuit board, and wherein the second electrically conductive layer is separated from the first electrically conductive signal layer by at least one second dielectric layer, the improvement further beneficially comprises a second cavity in the electronic circuit board extending through the second electrically conductive layer and the at least one second dielectric layer so as to expose at least the first and second portions of the plurality of electrically conductive pads within the second cavity. The second cavity is beneficially sized to accommodate the second electronic component therein. Also, the second cavity is beneficially sized so as to be larger in lateral dimension than the first cavity. Further, the second electrically conductive layer is typically an electrically conductive signal layer or an electrically conductive power/ground plane layer. In such a case, a third electronic component, that is stacked over the second electronic component, can make electrical contact with the second electrically conductive layer. The third electronic component can be an electrically conductive shield for shielding electromagnetic interference to and from the first and second electronic components. In this case, the second electronic component is typically either an integrated circuit component or a discrete component.
In accordance with still further aspects of the present invention, wherein the electronic circuit board is a double-sided electronic circuit board, wherein the cavity is a first cavity on a first side of the electronic circuit board, wherein the dielectric layer is a first dielectric layer, wherein the electrically conductive signal layer is a first electrically conductive layer having a first plurality of electrically conductive pads formed therein, wherein the electronic circuit board has a second electrically conductive signal layer formed on a second dielectric layer, wherein the second electrically conductive signal layer has a second plurality of electrically conductive pads formed therein, and wherein the second dielectric layer is disposed beneath the second electrically conductive signal layer relative to a second side of the electronic circuit board, the improvement further comprises a second cavity on the second side of the electronic circuit board extending through the second electrically conductive signal layer and the second dielectric layer. The second cavity is beneficially sized to accommodate a third electronic component therein such that at least one third electrical connection may be formed between the third electronic component and a first portion of the second plurality of electrically conductive pads, and at least one fourth electrical connection may be formed between a fourth electronic component, which is stacked over the third electronic component, and a second portion of the second plurality of electrically conductive pads. In such a case, the second cavity can be located substantially opposite the first cavity in the electronic circuit board.
In an alternative embodiment, the technique is realized as a method for increasing electronic component density on an electronic circuit board. The electronic circuit board has an electrically conductive signal layer formed on a dielectric layer, wherein the electrically conductive signal layer has a plurality of electrically conductive pads formed therein. The method comprises forming a cavity in the electronic circuit board extending through the electrically conductive signal layer and the dielectric layer. The cavity is beneficially sized to accommodate a first electronic component therein such that at least one first electrical connection may be formed between the first electronic component and a first portion of the plurality of electrically conductive pads, and at least one second electrical connection may be formed between a second electronic component, which is stacked over the first electronic component, and a second portion of the plurality of electrically conductive pads.
In accordance with other aspects of the present invention, the cavity may formed by etching the cavity in the electronic circuit board. For example, the cavity may be etched by photolithographically etching the cavity in the electronic circuit board, or plasma etching the cavity in the electronic circuit board. Alternatively, the cavity may be formed by milling the cavity in the electronic circuit board. For example, the cavity may be formed by laser ablating the cavity in the electronic circuit board. Alternatively still, the cavity may be formed by prefabricating at least one of the electrically conductive signal layer and the dielectric layer such that the cavity is formed upon assembly of the electrically conductive signal layer and the dielectric layer in the electronic circuit board.
In accordance with further aspects of the present invention, wherein the cavity is a first cavity, wherein the dielectric layer is a first dielectric layer, wherein the electrically conductive signal layer is a first electrically conductive layer, wherein the electronic circuit board has a second electrically conductive layer disposed above the first second electrically conductive layer within the electronic circuit board, and wherein the second electrically conductive layer is separated from the first electrically conductive layer by at least one second dielectric layer, the method further beneficially comprises forming a second cavity in the electronic circuit board extending through the second electrically conductive layer and the at least one second dielectric layer so as to expose at least the first and second portions of the plurality of electrically conductive pads within the second cavity. The second cavity is beneficially sized to accommodate the second electronic component therein.
In accordance with still further aspects of the present invention, wherein the electronic circuit board is a double-sided electronic circuit board, wherein the cavity is a first cavity on a first side of the electronic circuit board, wherein the dielectric layer is a first dielectric layer, wherein the electrically conductive signal layer is a first electrically conductive layer having a plurality of electrically conductive pads formed therein, wherein the electronic circuit board has a second electrically conductive signal layer formed on a second dielectric layer, wherein the second electrically conductive signal layer has a second plurality of electrically conductive pads formed therein, and wherein the second dielectric layer is disposed beneath the second electrically conductive signal layer relative to a second side of the electronic circuit board, the method further comprises forming a second cavity on the second side of the electronic circuit board extending through the second electrically conductive signal layer and the second dielectric layer. The second cavity is beneficially sized to accommodate a third electronic component therein such that at least one third electrical connection may be formed between the third electronic component an a first portion of the second plurality of electrically conductive pads, and at least one fourth electrical connection may be formed between a fourth electronic component, which is stacked over the third electronic component, and a second portion of the second plurality of electrically conductive pads.